almost xy-chain with r2c4(89=3); r78c8<>8
If r2c4=89: (8)r8c7=(8)r2c7-(8=9)r2c4-r5c4=r6c5-(9=8)r6c8;
If r2c4=(3): (3)r2c4-r7c4=r8c5-(3=8)r8c7;
...
I would appreciate any suggestion how to combine the two statements for the almost xy-chain.

I see no clever way to convert the net to a chain. I suppose this does you no good but, in modernized nice-loop notation, it would look like this:

How come you cannot use the Kite in r7/c7 to eliminate the 3 in r2c4? Then why isn't that an XY Chain, starting at r8c7: 83-38-89-97-79-98; & r78c8<>8?

I tried something different using a UR & 2 kites, but did not see the XY Chain. Instead I tried looking for an almost pattern & chose an ANP in r4c3; 89-6. 6 led to a contradiction & 89 solved the puzzle. Was I just lucky & do I have an incorrect understanding of these techniques?